1. Field of the Invention
The present invention relates to an image forming apparatus capable of glossing toner images formed on both a front side and a back side of a recording material.
2. Description of the Related Art
The following image forming apparatus is widely used. Specifically, a colored toner image and a transparent toner image are formed on a recording material in an image forming portion using an electrophotographic process, and the toner images are heat-fixed in a fixing portion (Japanese Patent Application Laid-Open No. H09-200551).
As an image forming apparatus for forming a colored toner image, the following image forming apparatus is widely used. In this image forming apparatus, a re-conveying path is provided for re-conveying a recording material having a front side, on which the toner image is fixed, to the image forming portion after reversing the front side and a back side of the recording material. In this manner, the toner image is also formed and fixed on the back side of the recording material.
Further, another image forming apparatus including a glossing portion for performing a glossing process for re-heating a toner image fixed onto a recording material to increase glossiness of the toner image has been put into practical use.
Japanese Patent Application Laid-Open No. H09-200551 describes an image forming apparatus including a transparent image forming portion for forming a transparent toner image and a colored image forming portion for forming a colored toner image, which are arranged along a recording material conveying member (or an intermediate transferring member).
Japanese Patent Application Laid-Open No. H04-362679 describes a glossing portion for heating and pressurizing a recording material bearing an unfixed toner image, which is brought into close contact with an endless fixing belt made of a heat-resistant film. In this glossing portion, after the toner image is forcibly cooled by a cooling portion to be solidified while the recording material remains in close contact with the fixing belt, the recording material, on which the toner image is fixed and solidified, is self-stripped from the fixing belt. An image surface is solidified after a smooth surface profile of the fixing belt. Thus, the smooth image surface excellent in glossiness can be obtained.
Japanese Patent Application Laid-Open No. 2007-332281 describes an image forming apparatus dedicated for transparent images. This image forming apparatus includes a fixing device and an image forming portion for a transparent toner image, and is connected to a later stage outside a housing of a full-color image forming apparatus.
For the glossing process of the toner images on both the front side and the back side of the recording material, it is desirable to provide the re-conveying path for conveying the recording material to the image forming portion after the front side, which has already been subjected to the glossing process in the glossing portion, and the back side of the recording material are reversed to automatically perform the glossing process on both the front side and the back side of the recording material.
However, if the glossing portion is provided downstream of the image forming apparatus, the size of the image forming apparatus is increased in a direction of conveyance of the recording material. Moreover, if the re-conveying path is provided for re-conveying the recording material having the glossed front side to the image forming portion, the size of the image forming apparatus is further increased in the direction of conveyance of the recording material.